This invention relates to isostatic processing of compactible materials.
Cold isostatic pressing is one process of choice for forming components from particulate materials. In cold isostatic pressing, a powder charge is loaded into an elastomeric mold (called a "bag"). The bag can be considered as a hermetically sealed pressure transfer membrane. The bag is sealed after filling, positioned within the containment vessel, and is exposed to a fluid environment.
The bag may be part of the pressure vessel (dry bag process) or may be a separate, independent unit placed within the pressure vessel (wet bag process). In either case, a mandrel may be included within the bag to aid in forming details on the resulting pressed material
In operation, the fluid is pressurized and in turn applies a hydrostatic pressure to the bag. If a mandrel is included inside the bag, then the pressure compacts the powder against the mandrel. Upon completion of the pressing process, the vessel and bag are opened and the part (called a "compact") is separated from the mandrel. The compact is then thermally treated, sintered, to increase strength through diffusion bonding.
This process results in near net shaping of components with uniform as-pressed densities in addition to inherent advantages of particulate materials processing. Isostatic pressing is also advantageous for forming components with large cross-sectional areas, or components with large length-to-diameter ratios, since the process is limited only by the capacity of the pressure vessel.